Free schools, set up by parents and other groups, are state-funded but operate outside local authority control.

They were established under a policy pioneered by Education Secretary Michael Gove and since September 2011 more than 170 have opened across England.

Currently free schools have discretion over what to teach, but in his speech to a school in north London on Thursday, Mr Clegg will ask: "What's the point of having a national curriculum if only a few schools have to teach it?"

Last week, the head teacher of a free primary school in London, who was still studying for her postgraduate certificate in education, stood down following criticism from Labour councillors.

There was also controversy when the al-Madinah free school in Derby was judged by the education watchdog Ofsted to be "inadequate".

Michael Gove and David Cameron's divisive Free Schools programme is unravelling for all to seeTristram Hunt, Shadow education secretary

In his speech, Mr Clegg will say: "I'm proud of our work over the last three years to increase school autonomy, which, in government with the Conservatives, has been through the academies programme."

But he will go on to question "aspects of schools policy currently affected by the priorities of the Conservative Party which I would not want to see continue".

Mr Clegg will add: "Whilst I want to give schools the space to innovate, I also believe every parent needs reassurance that the school their child attends, whatever its title or structure, meets certain core standards of teaching and care. A parental guarantee, if you like."

The deputy prime minister told Sky News he was a supporter of free schools, but his concern was about maintaining standards.

Coalition 'failure'

A Downing Street spokesman said earlier that, as recently as last week, the Lib Dem schools minister David Laws had said he was "100% behind the coalition's free schools policy, which makes Nick Clegg's comments all the more surprising".

Lib Dem sources have told the BBC that Mr Clegg argued for his proposed changes in cabinet but they were blocked by the education secretary.

But Mr Clegg said current education policy was "something for Mr Gove" to handle and that he did not interfere in the workings of his department.

Under plans announced by Labour, parent groups and other organisations would be able to set up schools outside local council control, although local authorities would have greater powers to intervene when there were concerns about standards.

On Sunday, shadow education secretary Tristram Hunt said: "Michael Gove and David Cameron's divisive Free Schools programme is unravelling for all to see.

"But Nick Clegg is locked-in to this failure too. It is his policies that have led to the mess we saw at the al-Madinah Free School earlier, the looming crisis in teacher recruitment and the 141% rise in unqualified teachers since 2010."

A Department for Education spokesman argued that free schools were "raising standards and giving parents more choice".

He said the government was not going to take away the freedom free schools have for teachers to "set their own curriculum, decide how they spend their money and employ who they think are the best people for the job".